#include <stdio.h>
#include <algorithm>
#define pdd pair <double,double>
#define x first
#define y second
#define NMAX 120005
using namespace std;
int n,r;
pdd A[NMAX],st[NMAX];
void read()
{
	scanf("%d",&n);
	int i;
	for (i=1; i<=n; i++)
		scanf("%lf%lf",&A[i].x,&A[i].y);
}
inline bool comp(pdd a,pdd b)
{
	if (a.y<b.y)
		return 1;
	if (a.y>b.y)
		return 0;
	if (a.x<b.x)
		return 1;
	return 0;
}
inline int semn(pdd a,pdd b,pdd c)
{
	double A=a.y-b.y;
	double B=b.x-a.x;
	double C=a.x*b.y-b.x*a.y;
	return (A*c.x+B*c.y+C)<0;
}
void solve()
{
	int i;
	st[++r]=A[1]; st[++r]=A[2];
	for (i=3; i<=n; i++)
	{
		while (r>=2 && semn(st[r-1],st[r],A[i])) r--;
		st[++r]=A[i];
	}
	for (i=n-1; i>=1; i--)
	{
		while (r>=2 && semn(st[r-1],st[r],A[i])) r--;
		st[++r]=A[i];
	}
	r--;
	printf("%d\n",r);
	for (i=1; i<=r; i++)
		printf("%lf %lf\n",st[i].x,st[i].y);
}
int main()
{
	freopen("infasuratoare.in","r",stdin);
	freopen("infasuratoare.out","w",stdout);
	read();
	sort(A+1,A+n+1,comp);
	solve();
	return 0;
}